(Pin,4508) How should the VPP pin be handled? [2007/08/09]

Question:

(Pin) How should the VPP pin be handled? [2007/08/09]

Answer:

The VPP pin is a power supply input pin of the on-chip QzROM, and is also used as the CNVSS pin.
When programming the on-chip QzROM, VPP pin impedance is driven low to allow the programming current to flow, and as a consequence noise can penetrate easily.
Noise tolerance can be improved by inserting a 5 kΩ resistor in series as close as possible to the CNVSS/VPP pin and connecting to the VSS pin. (#106687)